The present invention relates to a calligraphic character printer and more particularly to a method and apparatus for generating a compensating voltage useful in performing writing from a moving carriage.
Calligraphic character writing systems are known in which a pen or stylus, together with driving servo mechanisms, are transported on a carriage from character position to character position. As each position is traversed, the servo mechanisms are energized to effect tracing out of the desired character. In the copending and coassigned application of Richard M. Ulvila entitled High Speed Character Writer, a system for writing from a moving carriage is disclosed and generically claimed. The present invention pertains to an improved and presently preferred implementation of the general scheme claimed in that copending application.
As is understood, the vectors or line segments which make up a character will typically be stored in digital form in digital memory devices. So-called read only memories are usually preferred, packaged in a form which permits them to be easily exchanged, e.g. to effect the changing of character fonts. In the prior art character writing or printer system as disclosed, however, it appears that the carriage is moved from one position to the next and stopped to allow writing of each character. This then permits the vectors which typically make up each character to be defined with respect to a fixed frame of reference. While the possibility of writing while the carriage is moving has been suggested e.g. in the Brescia patent, no structure implementing this function is disclosed. Clearly, writing from a moving carriage has a substantial advantage in total throughput of the machine since the time spent accelerating and decelerating the carriage is deducted from the time available for writing. This loss of time sets an upper limit on the overall speed of the device which limits throughput no matter what improvements are made in the speed of the servomechanisms which drive the pen and stylus. As will be understood by those skilled in the art, the coding of vectors in digital form could be implemented so that the vector orientations themselves take into account the moving frame of reference. In this way the character resulting from writing from a moving carriage would have the desired shape notwithstanding the moving frame of reference. However, as will also be appreciated by those skilled in the art, such a compensation would be fixed in the original coding of each character and would be valid for a single carriage speed only.
Among the several objects of the present invention may be noted the provision of a high speed calligraphic character writer; the provision of such a character writer in which writing is effected from a carriage while the carriage is in motion; the provision of such a writer in which writing is performed by a stylus driven in transverse directions by a pair of servomotors carried on a carriage which is moving at a freely selectable velocity; the provision of such a system which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.